In the art of RF discharge waveguide lasers, summarized in U.S. Pat. No. 4,169,251, issued to Laakman on Sept. 25, 1979, the length of the waveguide fed by a single connector has been limited to .lambda..sub.m /4 where .lambda..sub.m is the RF wavelength of the power supply feed in the dielectric material adjacent to the optical cavity. The reason for this limitation has been that the power fed into the waveguide travels from the feed point to the ends and is there reflected causing interference between a return wave and a traveling wave, so that the field along the discharge length is highly nonuniform. The only method known to the prior art for extending the length of the waveguide, and thus increasing the power which may be obtained from the laser, has been to feed power into the optical cavity at more than one point. The problem with this approach has been that great care is needed to adjust the phases at different feed points so that destructive interference between the several feed points does not occur. The Laakman patent referred to above teaches the necessity for multiple feeds and also the necessity for reactive termination of the waveguide ends.
An RF excited waveguide laser upon which the subject invention of this patent application is an improvement is illustrated in patent application Ser. No. 214,858, now U.S. Pat. No. 4,363,126 assigned to the assignee hereof and incorporated herein by reference, which discloses an RF excited discharge laser having a single feed point and an inductor connected in parallel with the RF electrodes so that the optical cavity is an RF tuned circuit. This application teaches away from the subject invention in that it also states that the length of a RF laser is limited to approximately .lambda..sub.m /4.